Inclusion Criteria:

Study participants eligible for inclusion in this study must meet all of the following criteria:

1. Prior use of tisagenlecleucel treatment in CTL019 clinical trial setting or post-marketing/commercial tisagenlecleucel setting as outlined for Cohort 1 and Cohort 2
2. Confirmed diagnosis of secondary malignancy of T-cell origin via redacted pathology report and/or clinical confirmation by the Principal Investigator/clinician responsible for enrolling the participant. Clinical judgement may be required in cases where the diagnosis is not clearly confirmed in the redacted pathology report. There also may be cases in certain site/countries, where sharing the redacted pathology reports is not allowed, hence the clinical diagnosis will be allowed for eligibility.
3. Availability of existing secondary malignancy of T cell origin specimen(s) from tissue, and/or bone marrow aspirate sample(s) and/or blood or DNA extracted from blood (with confirmed T-cell malignancy diagnosis in the sample provided) collected during routine standard of care during the secondary malignancy of T-cell origin diagnosis. Often, only a limited amount of the appropriate sample(s) may be available. For the testing process, a specimen containing the malignant T-cells for the secondary malignancy of T-cell origin must be present. The type of specimen/sample for testing is determined based on the location of the secondary malignancy of T-cell origin. For example, bone marrow aspirate and/or blood and/or bone marrow biopsy may be needed for analysis for a secondary malignancy of T cell origin when the malignant T cells are present in blood and/or bone marrow, and tissue such as a lymph node location or cutaneous or other location is needed when this is the region of the body affected by the secondary malignancy of T-cell origin. Blood, (even if NOT involved with the T cell malignant cells) when available, may also be used for comparison to the tissue/bone marrow used for the analysis. Novartis has established ranges of CAR transgene level in blood for all 3 pivotal trial indications at specific time points. This is used for comparison.

See laboratory manual for detailed instructions. The following types of samples are recommended for collection if available/pre-existing:
1. Tumor tissue (FFPE block (ambient temp), unstained slides (ambient temp), or bone marrow aspirate in EDTA or blood in EDTA and frozen, if malignant T-cells present)
2. Peripheral blood EDTA frozen- to be used when available and either not involved with T-cell malignancy for comparison to the tumor sample provided and/or if peripheral blood has circulating malignant T cells for analysis.
3. Bone marrow aspirate EDTA frozen if involved with secondary malignancy of T-cell origin.
4. DNA extracted from blood or bone marrow aspirate stored frozen
5. Bone marrow biopsy if malignant T-cells are present (FFPE block, unstained slides, ambient temperature)
4. Signed informed consent. For participants who have died, it is acceptable for clinical/academic sites to use a previous biospecimen research consent, or to have an appropriate family member or designated representative to provide consent on behalf of the participant as per local regulations.

Exclusion Criteria:

Study participants meeting any of the following criteria are not eligible for inclusion in this study:

1. Ongoing enrollment on Novartis sponsored CTL019 interventional or LTFU clinical trial
2. Cases where there is no existing available specimens that include the secondary malignancy of T cell origin (tumor tissue and/or existing blood and/or bone marrow and/or DNA from blood for testing)
3. Cases where informed consent is not possible.